Key takeaways
Melanomas are tumors of pigment-producing cells, known as melanocytes. Formation of melanoma involves a complex combination of genetic and environmental factors and may be malignant or benign.
- Feline melanoma usually develops in the mouth, eyes, or skin
- Oral melanomas present with bleeding from the mouth, a bad smell, or difficulty swallowing
- Melanomas of the eye are usually visible and trigger eye inflammation
- Skin melanomas are normally seen or felt during grooming and often have no additional symptoms
- Skin melanomas most frequently occur on the head, tail, or legs in cats
- Investigation involves physical examination alongside biopsy or needle aspiration, and diagnostic imaging to assess for metastasis
- Treatment involves complete removal of the tumor; radiation therapy my also be beneficial
- Prognosis is dependent on the type of melanoma and is guarded to poor
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A closer look: Melanoma in Cats
Melanomas behave differently depending on location. Cutaneous melanomas sometimes ulcerate and trigger irritation but most cases have no additional symptoms.
Oral melanomas often present later in the disease process as there may be no additional symptoms in the early stages. Symptoms develop due to the size of the tumor and may impact chewing or swallowing.
Ocular melanomas disrupt the symmetry of the eyes and result in secondary inflammation and visible changes to the eye.
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Risk factors
Melanoma is a rare condition in cats and is most commonly seen in cats over 10 years old. As with all cancers, environmental and genetic risk factors are likely.
Ultraviolet light exposure is unlikely to contribute to melanoma formation in cats, in spite of it being a causative factor in humans. There is evidence that repeated trauma from scratching, biting and licking may play a role in cutaneous melanoma in cats, although this is unconfirmed.
Prognosis varies depending on location. Cutaneous melanomas are more likely to be benign and early diagnosis with removal is often curative. Melanoma of the eyes or mouth have more variable outcomes. Some cases of ocular melanoma are benign or very slow growing. Oral tumors in cats are rarely benign, most cases are highly aggressive with survival times as short as 6 weeks. Cats with iris changes, difficulty chewing or swallowing, new skin lumps, or changes in pigmentation require prompt veterinary assessment.
Possible causes
Melanoma has no specific identifiable disease mechanism. Most tumors involve a complex interplay of genetic and environmental factors.
Main symptoms
Symptoms of melanoma depend on location:
Cutaneous (skin) melanoma is most common on the lips, nose, ear tips, tail, and leg. These often appear as solitary, raised, pigmented mass (in some cases the mass is not pigmented) that may be ulcerated.
Testing and diagnosis
Investigation of melanoma involves sampling of the mass and detection of secondary spread. Diagnostic tools include
- Physical examination
- Needle aspiration
- Biopsy
- Blood work
- Diagnostic imaging
Steps to Recovery
Treatment options include surgical removal of the tumor(s), up to and including removal of the affected eye, if necessary. Radiation therapy may also be recommended.
There is a vaccine labeled for treatment (not prevention) of melanoma in dogs with oral melanoma. It is used in conjunction with surgery and/or radiation therapy and is used off-label in cats by some veterinary oncologists. More research is needed regarding efficacy in cats, but current research shows potential.
Melanoma is a serious condition but the prognosis varies significantly depending on tumor location and whether the tumor is benign or aggressive.
Benign melanomas are often curable with complete surgical removal. Cutaneous melanomas are more likely to be benign than other forms.
Aggressive melanomas spread rapidly to the liver and lungs and often carry a poor prognosis. Ocular melanomas are usually malignant, but early diagnosis and surgery improves survival times.
Oral melanomas are normally aggressive and the tendency of them having late diagnosis impacts survival times, which are as short as 6 weeks. Many cats with melanoma in the mouth are euthanized due to poor quality of life.
Prevention
Prevention of melanoma is not possible due to the wide variety of contributing factors
Is Melanoma in Cats common?
Melanoma is a rare type of tumor in cats. Ocular melanomas are the most common primary eye tumor in cats.
Typical Treatment
- Treatment of secondary complications
- Radiation therapy
- Surgical tumor removal
- Removal of the affected eye
